1. Field of Invention
The invention relates to a bone repair material that is useful in the repair of bone defects, in particular in the repair of defects filled with aqueous body fluids such as blood.
2. Description of Related Art
From WO03/082365 a kneadable and formable bone replacement mass is known based on ceramic particles having a diameter in the range of 0.1 mm to 5.6 mm suspended in a hydrogel. This mass has the disadvantage that hydrogels for human use are very expensive. Another disadvantage connected with hydrogels is the fact that sterilization via gamma-irradiation destroys the polymer chain, hence reducing the average molecular weight and decreasing the polymer viscosity.
From the WO 99/20237 a stomatic composition based on hydroxyapatite nanoparticles is known which may include further components such as various abrasive materials (0 to 25%). These abrasive materials may consist of anhydrous dicalcium phosphate, dicalcium phosphate dihydrate, and calcium carbonate. However, there is no indication in this prior art document about the preferred size range for these abrasive materials. Also it does not mention the use of β-tricalcium phosphate. Moreover, this prior art cement is proposed only for use in the field of stomatology and not of bone repair. The main disadvantage of this known material is that it does not allow the surrounding bone cells to anchor and to proliferate.
From two articles of JJC Arts et al.:                “The use of a bioresorbable nano-crystalline hydroxyapatite paste in acetabular bone impaction grafting”. Biomaterials, In Press, and        “Cemented cup stability during lever-out testing after acetabular bone impaction grafting with bone graft substitutes mixes containing morselized cancellous bone and tricalcium phosphate-hydroxyapatite granules” published in Proc Inst Mech Eng [H] 2005; 219:257-67, it is known that a nano-crystalline paste (40 weight-% water) can be combined with biphasic calcium phosphate granules (80% β-TCP, 20% HA). The latter authors used very large granule diameters, i.e. 1.5-2.0 mm, 4-6 mm, and 4-8 mm granules combined with a very small nano-crystalline paste content (up to 33 volume-%), because they wanted to use the granular paste for impaction grafting. Results showed however that a 33 volume-% paste content—for that special field of application—was too much to provide an adequate initial cup stability and therefore the authors were led to prefer lower contents in the region of 10% for the nano-crystalline paste. For these reasons the authors did not even consider the possibility of using a higher content (over the 33 volume-%) of nano-crystalline paste.        
Accordingly, it is the principal object of the present invention to provide a bone repair material overcoming the above disadvantages and not being based on hydrogel.